JPH047558A - Electrophotographic sensitive body and method for removing remaining charge - Google Patents

Abstract

PURPOSE:To prevent the degradation of the sensitivity by nearly equalizing the ionized potential of a conductive base to the ionized potential of a charge transfer layer or making the ionized potential of the former layer larger than that of the latter. CONSTITUTION:In a photosensitive body successively forming the charge transfer layer, a charge generating layer and a surface protective on the conductive base, the ionized potential on the conductive base is nearly equalized to the ionized potential of the charge transfer layer or is made larger than that. Thus by equalizing the ionized potentials of the base and the charge transfer layer, a positive hole is implanted from the base and then an inner remaining electron is offset. But since a positive hole implantation from the base occurs when the surface is charged negatively, an image exposure is performed as a removing method of the remaining charge in the inside of photosensitive body after it is charged positively. Subsequently a development by a toner, transfer to a copying sheet and cleaning of a remaining toner are carried out and before the positive charge is electrostatically changed for the following copying, the operation charging the surface negatively is performed. Thus, the degradation of the sensitivity is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to copying printers and facsimile machines, and more particularly to an electrophotographic photoreceptor suitable for an electrophotographic printer using a laser imagewise line scanning method.

Conventional technology Copying methods using electrostatic copying methods, printers, etc.
Although photoreceptors based on chalcogenide, an inorganic material, were used, organic photoreceptors using organic materials have made remarkable progress in terms of sensitivity and longevity, and are now the mainstream.还Negatively charged photoreceptors, in which charge-generating and charge-transporting layers are sequentially laminated on a conductive substrate, are most commonly used and studied.However, large amounts of ozone are emitted from these devices used in offices. The negative effects on the human body are considered to be a problem, and the development of positively charging type photoreceptors is currently actively underway. There are single-layer structures with dispersed carbon dioxide, and those with a charge generation layer near the surface and a surface protection layer on top. types are potentially being studied. (
JP-A-63-305364 JP-A-1-1856
Problems to be Solved by the Invention (No. 48, etc.) A photoreceptor having a charge generation layer near its surface (
When a positive charge is applied to the surface, the eight holes of carriers generated by light transfer to the charge transport layer below.
The corresponding electrons must pass through the surface protective layer and cancel out the positive charge on the surface.II~ This resistance Force that provides electron transport ability as a surface protective layer＼ Necessity to control the resistance value to allow electrons to escape to the surface occurs. To increase electron transport ability, the surface protective layer contains an additive with electron transport ability.
Disperse conductive filler. However, when the surface resistance of the surface protective layer decreases below a certain value, charge leaks in the in-plane direction of the surface, destroying the latent image, resulting in so-called image deletion or image blurring. The surface resistance of this item is 10
It is inevitable that the resistance will be as high as 13 to 101'Ω/mouth.

In addition, the surface protective layer must be able to withstand the sliding action of cleaning blades, etc., and the strength requires a certain degree of hardness. It does not interfere with the hardening of the layer and reduces its strength. Therefore, it is difficult to add a conductivity control agent to the surface protective layer. Means for solving the problem that the conductive substrate remains inside the photoreceptor, causing deterioration of sensitivity and increasing dark decay.To solve the above problems, the present invention provides a conductive substrate. A photoreceptor on which a charge transport layer, a charge generation layer, and a surface protective layer are sequentially formed, wherein the ionization potential of the conductive substrate is approximately equal to the ionization potential of the charge transport layer, and is characterized in that the ionization potential of the conductive substrate is approximately equal to the ionization potential of the charge transport layer. The present invention provides an electrophotographic photoreceptor.

In addition, according to the present invention, the electrophotographic photoreceptor is charged with a positive polarity charge, a latent image is formed in an imagewise manner by exposure, the image is visualized with charged particles, and after the charged particles are transferred to copy paper, the next time the electrophotographic photoreceptor is charged with a positive polarity charge. The present invention provides a residual charge removal method for reversing the surface potential of the electrophotographic photoreceptor with a negative charge.

Based on the results of research, the inventors (friends) came up with the idea of injecting holes from the substrate side as a means of canceling out the electrons inside the photoreceptor.To inject holes from the substrate ( It is necessary to make the ionization potential of the substrate and the ionization potential of the charge transport layer similar to each other.The inventors (
Using Au and A1, which have different ionization potentials, as substrate materials (\A charge transport layer was provided on these metals (if a negative charge was applied to the surface and the attenuation of the surface potential was investigated),
When a charge transport layer was provided on top of U, the attenuation was large, confirming that holes were injected from the substrate material.The ionization potential was measured using an ultraviolet irradiation low energy spectrometer.J% Au was 4. 85eV, AI is 4.2'5e
V, the charge transport layer obtained a value of 5.05 eV.
Holes are injected from the substrate to cancel out the internal residual electrons. After that, perform image exposure.After this,
Developing images with toner ([A] Cleaning the toner remaining on the copy paper before charging with a positive charge for the next copy. Charging the surface with a negative charge. Reverse development. When using the above method (this is done with top transfer).

EXAMPLE An example of the present invention will be described in detail below. The base material of the photoreceptor (companion) is a metal such as iron, polyamide resin, phenolic partner 1, resin such as polyethylene, vinyl chloride, paper, glass, etc. Metals are conductive and can be used as they are. Can be used.Generally Aluminum alloy is often used in consideration of workability since it is used in a cylindrical shape.L JIS3003
& There are many 6063 series.

Resin, paper, glass, etc. can be made conductive by coating them with conductive paint that does not give them conductivity, or by mixing conductive fillers such as carbon, oxide ore, indium oxide, etc. into the resin. In the present invention, the coatability after obtaining the base material, the immediate hg
In order to develop conductive paints that do not dissolve in solvents when applying the light layer, resins such as polyamide and polyvinyl alcohol that are soluble in water and alcohol solvents can be used as binder resins for paints. Resin (for example, acrylic or butyral resin cured with melamine resin, etc.) is used, and a conductive filler is dispersed in these resins to form a paint.Resistance required as a base material for a photoreceptor that satisfies electrophotographic characteristics. To obtain the volume resistivity of 101 to lQI ItΩ・ by changing the amount of filler dispersed in the resin.
A film of cm is formed on the substrate. When the base material is metal (the volume resistance value can be set high), the inventors c! The conductive layer formed on the base material is made of alcohol-soluble polyamide resin (
Toshi Co., Ltd. Product name CM-8000) 155 parts by weight of antimony-doped tin oxide (Mitsubishi Metals Co., Ltd., product name T-1) 5 parts by weight was dissolved in At-Alcohol and dip coated onto an aluminum tube. After drying at 80 degrees for 1 hour, a conductive layer with a thickness of 1 μm was obtained.The volume resistivity of this film was 103Ω・Cm. The charge transport layer is formed by containing a low molecular weight charge transport material in a high molecular weight binder.The binder resins usually used are polycarbonate resin 1 polyarylate resin polyester resin acrylic resin thermoplastic resin such as styrene resin thermosetting resin Use.

As a charge transport material (Table Alkyl group Amino group Imino group Polycyclic aromatic compounds such as anthracene, phenanthrene, pyrene, etc. having electron-donating properties such as imide group, or derivatives containing them Indole oxa sheets k Carba sheets k Pyrazoline, imida sheets k Heterocyclic compounds such as oxacia sheet k thiazo-/lz, ) lyazole or derivatives containing the same are used. When forming a charge generation layer on a charge transport layer as in the present invention, a binder resin and a solvent that dissolves the binder resin must be selected so that the charge generation layer is formed without damaging the charge transport layer. It is also required that the charge transport layer has good compatibility with the charge transport material and that a film of 50 μm or less can be stably formed by a film forming method such as dip coating, spin coating, or spray coating. Film thickness LL
, the shape of the charger, the polarity of the discharge, the process speed of the grid, etc., are comprehensively judged and determined. Usually, a film thickness of 20 to 30 μm is used. The blending ratio of the charge transporting material and the binder resin has a strong influence on sensitivity, and the blending ratio that provides the best sensitivity must be selected. The content is preferably 60% or less by weight,
In addition, as a charge transport layer, it is better to use a high molecular weight resin such as polyvinylcarbazole or polysilane as is.
As a charge transport material, 1 part by weight of 1,1-bis(P-diethylaminophenyl)-4,4-diphenyl-1,3-butadiene was dissolved in 9 parts by weight of methylene chloride, and then applied onto the above-mentioned conductive film. Film formed by dip coating method L 8
Drying was carried out for 1 hour at 0 degrees Celsius to obtain a 20 μm film.The charge generation layer formed on the charge transport layer described above consists of a charge generation substance, a charge generation aid, a binder resin, etc.The charge generation substances are phthalocyanine, azo, etc. Organic pigments and paints such as cyanine-based materials are used. Phthalocyanine-based materials are the main materials for laser beam printers, and α, β, ε
It is known that different crystal forms such as , τ and X types exist, and the central element of the phthalocyanine molecule 5 HlC
It is known that there are many such as u, Ti, Vo, etc. Research is currently being conducted from the other side in order to obtain highly sensitive materials. Added as a charge generation aid (Y) for the purpose of increasing the carrier generation quantum efficiency inside the charge interlayer and to prevent deterioration due to repetition.Added materials (Y) are mainly electron-donating materials and electron-accepting materials. There are also examples where the characteristics were improved by adding the charge transport layer mentioned above.
Use poly-〇- ester resin, butyral resin, acrylic resin, thermoplastic resin such as melamine resin, thermosetting resin, etc. The binder resin forms a local field due to the functional groups attached to its side chains, and also acts as a trap for electrons and holes, which affects the carrier generation and repeatability characteristics of the photoreceptor. Therefore, the selection of the binder for the charge generation layer is important. Mixing ratio of charge-generating substance and binder (determined based on photoreceptor sensitivity, repetition characteristics, etc.)Special C: - When the charge-generating layer is near the surface, ozone and paper components when using the photoreceptor It is necessary to pay attention to the deterioration caused by these stresses.In particular, positive or negative ions during charging are likely to act on charge-generating substances, and it is important to select a binder that protects charge-generating substances from these ions. Generally, based on the above points, the charge-generating substance is mixed in the binder in an amount of 10 to 70% by weight.The charge-generating substance and binder resin are made into a paint by ultrasonic dispersion, milling dispersion, etc. Considering that the charge generation layer exists near the surface layer, the inventors selected a binder from the viewpoint of suppressing moisture absorption from the surface.As a binder resin, a solvent-soluble fluororesin was selected. Examples of uses include copolymers of solvent-soluble fluororesins (such as fluoroolefins and ethylenically unsaturated monomers such as vinyl ethers, allyl ethers, and vinyl esters). Ethyl vinyl ether/lz, cyclohexyl vinyl ether and ethyl vinyl ether in weight%
Copolymerized in a ratio of 56:22:6:16, and the intrinsic viscosity measured at 30°C in tetrahydrofuran was 0.06.
dl/g of the fluorine-containing copolymer with t-butanol/n
The above-mentioned fluororesin (solid content concentration 50%), vinyl butyral resin (Sekisui Chemical Co., Ltd. product name Ko Sletsku BI (-3)) and 2-butanol were made into a fluororesin using a mixed solvent of butanol (30/70). and τ-type metal-free phthalocyanine in a weight ratio of 4:1:48:6, and then dispersed in a ball mill for 4 hours. -145-60 (solid content concentration 60%) was added, and the solid content ratio of τ-type metal-free phthalocyanine/solvent-soluble fluororesin/vinyl butyral resin/melamine resin was 6:2.
Add so that the ratio of 1 to 1 is 5%.
A film was formed on the charge transport layer described above by dip coating, and dried at 120 degrees for 1 hour to obtain a 0.20 μm film. Ruts generated by plasma during charging, such as ozone, NOx, etc. Must be stable against substances such as tungsten oxide and silicon oxide, and must be stable against substances such as tungsten oxide and silicon oxide. It is necessary that paper components such as chlorine ions are difficult to adhere to the surface during transfer. Examples of materials that have these properties include thermosetting acrylic resins, silicone resins, polyamide resins, and urethane resins.Invention In order to maximize the above-mentioned properties, urethane resin (condensate of polypropylene glycol and isophorone diisocyanate), silicone resin (partial condensate of methylsilanol), and hydrophobic silica (
Nippon Aerosil Co., Ltd., trade name R-974) was mixed in a weight ratio of 3:7:3, mixed and dispersed using 1-butanol, and then dip coated onto the charge generation layer described above. A film of 1.0 .mu.m was obtained by drying for 30 minutes at .degree. C..9 The photoreceptor produced as above was evaluated using a drum evaluation device.

Let me briefly explain the drum evaluation device. FIG. 1 shows a cross section of the drum evaluation device, in which 1 is a scorotron charger, 3 is an exposure device for exposing a tungsten lamp as a light source through a filter, 5 is a scorotron transfer charger, and 7 is 3. The Rikijo filter, which has a similar structure, is a static eliminator equipped with a bandpass filter that cuts light below 550 r+m. Reference numeral 9 denotes a cylindrical photosensitive drum, on which the above-mentioned photosensitive layer is formed on an aluminum alloy. The rotation direction of the drum is the first
It is rotated clockwise in the figure, and the rotation speed can be set arbitrarily. The distance between the grid of the scorotron type charger 1 and the scorotron type transfer charger 5 and the drum is set to 1 mm. The outer diameter of the photoreceptor drum 9 is 60 mm, and one rotation is 1
The surface potential of the photoreceptor drum is measured by rotating it in seconds to evaluate its characteristics. After passing through a scorotron charger 1, an exposure device 3, a scorotron transfer charger 5, and a static eliminator 7, the surface potential of the photoreceptor drum is determined by a vibrating capacitive surface potential sensor (manufactured by Trek). Model 344) was installed and monitored.The results are shown in Table 1. For comparison, we tested a model using an aluminum alloy as a base material and a model with a conductive layer coated on the aluminum alloy. It means the surface potential after being applied. The initial surface potential of the photoreceptor drum is 5oov. However, the Scorotron transfer charger 5 was not operated (℃ measurement environment was 20℃).
30% RH Table 1 Table 2 shows the results when the Scorotron type transfer charger 5 was operated and the potential on the surface of the photosensitive drum 9 was reversed to -300V. This is also compared based on the presence or absence of a conductive layer.

Table 2 As shown above, by newly applying a conductive layer L, once the surface potential of the photoconductor drum 9 is reversed to negative, the potential after exposure becomes low and good sensitivity characteristics are exhibited. A material having an insulating surface protective layer is expected to increase its volume resistance under low temperature and low humidity conditions.It is considered effective to actively offset the internal residual carriers as in the present invention.

Effects of the Invention As described above, the present invention has a structure in which the ionization potential of the conductive substrate is approximately equal to the ionization potential of the charge transport layer formed on the substrate, and the electrophotographic photoreceptor is charged with a positive charge. A latent image is formed image-wise by exposure, visualized by charged particles, and after the charged particles are transferred to copy paper, the surface potential of this electrophotographic photoreceptor is raised by negative charges before the next charging with positive charges. It is possible to provide a method for removing residual charges, which removes charges remaining inside an electrophotographic photoreceptor by injecting charges from a substrate.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a drum evaluation device according to an embodiment of the present invention. 1... Scorotron-type charging bolt 3... Exposure device 5... Scorotron-type transfer charging bolt 7... Static elimination device 9... Name of photoreceptor drum agent Patent attorney Shigetaka Awano et al. Figure 1 for 1 person! ST0TO0] 1%11TAI Exposure equipment SFOT0 type transfer evaporator Static elimination equipment Kotei drum

Claims (4)

[Claims] (1) A photoreceptor in which a charge transport layer, a charge generation layer, and a surface protective layer are sequentially formed on a conductive substrate, and the ionization potential of the conductive substrate is approximately equal to the ionization potential of the charge transport layer. is an electrophotographic photoreceptor characterized by its large size. (2) The electrophotographic photoreceptor according to claim 1, wherein the conductive substrate is a substrate in which conductive powder is dispersed in a resin. (3) The electrophotographic photoreceptor according to claim 1, wherein the surface protective layer has a surface resistance with no charge leakage in the in-plane direction under an environment of absolute humidity of 35 g/m^3. (4) After the electrophotographic photoreceptor according to claim 1 is charged with a positive charge, a latent image is formed in an imagewise manner by exposure, the image is visualized with charged particles, and the charged particles are transferred to copy paper. . A residual charge removal method, which inverts the surface potential of the electrophotographic photoreceptor with a negative charge before the next charging with a positive charge, and removes the charge remaining inside the electrophotographic photoreceptor.